examples: When linking to directories, append a '/' to the URL.

This works without it, but generates an extra redirect on the web server to
the same a URL with the '/' appended, so we might as well supply it ourselves
and remove the extra roundtrip to the server.

examples/template-category.html

@@ -31,7 +31,7 @@
       <nav class="breadcrumb">
         <ul>
           <li><a href="/@project_name@/">@project_name@</a></li>
-          <li><a href="/@project_name@/@category_name@">@category_name@</a></li>
+          <li><a href="/@project_name@/@category_name@/">@category_name@</a></li>
         </ul>
       </nav>
       <h1>@project_name@ examples: @category_description@</h1>